A circum-aural (around-the-ear) headphone includes an ear cushion for coupling the headphone transducer to the ear of a user, while providing an acoustic seal to form an acoustic pressure chamber with smooth and extended frequency responses within the audible band (i.e., between 20 Hz to 20 kHz). Sound reflections and modes in the chamber have an undesirable effect on perceived frequency response, particularly at high frequencies above 1 kHz. The design of the headphone transducer and the ear cushion affect the sound reflections.